width = 50;
longth = 32;
height = 20;
thickness = 5;

difference () {
    translate([0, 0, (width + thickness)/2])
        rotate([90,0,0]) difference () {
            cube([longth + thickness,
                    width + thickness,
                    height], center = true);
            cube([longth, width, height], center = true);
        }
    translate([0, 0, (thickness /2 )])
        cube([height*2, width, thickness * 4], center = true);
}
translate([0, 0, (height)/2]) difference() {
    cube([longth + thickness, width + thickness, height],
            center = true);
    cube([longth, width, height], center = true);

}
